USB Interface Power Supply Method and Power Supply Device for Time Division Multiple Access Load System

1. A USB interface power supply device for a time division multiple access load system, comprising: a USB interface, a soft-start circuit and a DC-DC direct current conversion circuit that are connected in sequence, wherein, an output of the DC-DC direct current conversion circuit supplies power to the time division multiple access load system, and the USB interface power supply device further comprises a capacitor, wherein: a first end of the capacitor is connected between the soft-start circuit and the DC-DC direct current conversion circuit, a second end of the capacitor is set to be grounded, and the capacitor is used for limiting an input current of the DC-DC direct current conversion circuit; a capacitance value of the capacitor is decided according to voltages of the capacitor when the time division multiple access load system works and does not work, a maximum current allowed to be output by the USB interface, an input voltage of the DC-DC direct current conversion circuit, a voltage and a current required by the time division multiple access load system, and working time of the time division multiple access load system within one time cycle, wherein a capacitance value of the capacitor being decided according to voltages of the capacitor when the time division multiple access load system works and does not work, a maximum current allowed to be output by the USB interface, an input voltage of the DC-DC direct current conversion circuit, a voltage and a current required by the time division multiple access load system, and working time of the time division multiple access load system within one time cycle comprises: the capacitance value being obtained through calculation with a following formula: C = ( U 0 × I 0 U i × η - I ) × Ton UC ⁢ ⁢ 1 - UC ⁢ ⁢ 2 ; wherein, UC1 is an initial voltage of the capacitor when the time division multiple access load system does not work, UC2 is a voltage of the capacitor when the time division multiple access load system works, U 0 is the voltage required by the time division multiple access load system, I 0 is the current required by the time division multiple access load system, U i is the input voltage of the DC-DC direct current conversion circuit η is a conversion efficiency of the DC-DC direct current conversion circuit, I is the maximum current allowed to be output by the USB interface, and Ton is the working time of the time division multiple access load system within one time cycle.

2. The device according to claim 1 , wherein, the USB interface power supply device further comprises a detection circuit and a baseband control circuit, wherein: the detection circuit is configured to: be located between the USB interface and the soft-start circuit, and detect whether an output voltage of the USB interface is lower than a preset threshold value; and the baseband control circuit is configured to: connect with the detection circuit at one end, and connect with the time division multiple access load system at the other end, and when the detection circuit detects that the output voltage of the USB interface is lower than the preset threshold value, reduce transmission power of the time division multiple access load system.

3. The device according to claim 2 , wherein, the capacitor comprises a capacitance group and a switch group, one end of the capacitance group serves as the first end of the capacitor, the other end of the capacitance group serves as the second end of the capacitor, the switch group is connected with the baseband control circuit, and the switch group turns on or turns off internal switch components of the switch group to control a capacitance value of the capacitance group according to control of the baseband control circuit.

4. The device according to claim 3 , wherein, the capacitance group comprises at least two parallel capacitances, and each capacitance is connected with a switch component in series, and all switches constitute the switch group.

5. A USB interface power supply method for a time division multiple access load system, comprising: after soft starting, a capacitor limiting an input current of a DC-DC direct current conversion circuit, wherein a capacitance value of the capacitor is decided according to voltages of the capacitor when the time division multiple access load system works and does not work, a maximum current allowed to be output by a USB interface, an input voltage of the DC-DC direct current conversion circuit, a voltage and a current required by the time division multiple access load system, and working time of the time division multiple access load system within one time cycle; and the DC-DC direct current conversion circuit performing voltage conversion, and supplying power to the time division multiple access load system, wherein a capacitance value of the capacitor being decided according to voltages of the capacitor when the time division multiple access load system works and does not work, a maximum current allowed to be output by a USB interface, an input voltage of the DC-DC direct current conversion circuit, a voltage and a current required by the time division multiple access load system, and working time of the time division multiple access load system within one time cycle comprises: the capacitance value being obtained through calculation with a following formula, C = ( U 0 × I 0 U i × η - I ) × Ton UC ⁢ ⁢ 1 - UC ⁢ ⁢ 2 ; wherein, UC1 is an initial voltage of the capacitor when the time division multiple access load system does not work, UC2 is a voltage of the capacitor when the time division multiple access load system works, U 0 is the voltage required by the time division multiple access load system, I 0 is the current required by the time division multiple access load system, U i is the input voltage of the DC-DC direct current conversion circuit, η is a conversion efficiency of the DC-DC direct current conversion circuit, I is the maximum current allowed to be output by the USB interface, and Ton is the working time of the time division multiple access load system within one time cycle.

6. The method according to claim 5 , wherein, the method further comprises: detecting whether an output voltage of the USB interface is lower than a preset threshold value; and if the output voltage of the USB interface is lower than the preset threshold value, reducing transmission power of the time division multiple access load system.

7. The method according to claim 6 , wherein, the method further comprises: after determining the capacitance value of the capacitor, by controlling on-off of switch components in a switch group connected with the capacitor, adjusting the capacitance value of the capacitor.

8. The method according to claim 7 , wherein, the capacitor comprises at least two parallel capacitances, and each capacitance is connected with a switch component in series.